I was wondering which whistles do better in the high octave without becoming shrill and louder or breaking up? I have tried high end whistles which do this. I know that it also depends on breathing. But some of the whistles must be easier to blow and more consistent in higher octaves. 
Being newer to the whistle I would appreciate any info. Thanks.
My Clarke Original handles the high notes the best out of any whistle I’ve ever used.
The Blackbird will do very well.
You’re doing your second hand information thing again Jim.
While the Blackbird is nicely balanced, it may not be the most forgiving whistle for someone who has trouble with breaking octaves : it requires a degree of breath-control to work well.
And I can tell because I have six of them here. How many have you played?
Many expensive whistles will get very loud in the second octave in my experience anyway.
My beloved tweaked O’Brien Feadog plays the octave very nicely, but not sure how much breath control it really takes, might take a lot. I guess the Sindt is a winner in that department, can handle some extra air in the second octave, without being overly loud.
‘I was wondering which whistles do better in the high octave without becoming shrill and louder or breaking up?’
Peter has written me about the Blackbird, that it is an effort
to capture the Gens that I played in the late 70s or so.
They had a lovely, sweet, birdlike top end.
I have every confidence in Jerry and Peter and MT
and of course I can hear the result on the clips they’ve
posted. No, the Blackbird is not like many whistles
I’ve played that are very shrill and loud upstairs
or break up. Even if it will take a bit of practice to get
it right, the Blackbird will do very well.
I’ll get sound clips posted as soon as I can prepare them. The Blackbird is designed for a birdlike voicing, especially in the upper register.
Best wishes,
Jerry
Yes, it’s an interesting question about what to do about it.
Some teachers (Cathal McConnell) recommend staccottoing
the notes on the top end, to reduce shrillness.
Any other suggestions? I’m actually struggling with this
right now as I have a couple of whistles that are
lovely till you get to the top two notes and then
they kill spiders.
got to love them—also my Clarke pro-(Copeland)-also sweetheart pros are great
My Mellow Dog is nice on the high end, but using it with the C body is exceptionally so. Very sweet, not shrill, and an easy player.
I also like my Every Whistle. It can be a bit shrill on the high A and B if the tone ring is all the way open, but it can be adjusted to keep that nicely in check. It takes more air pressure to play the second register cleanly, but I wouldn’t call it difficult.
Jason
Anything built by Mike Burke is sweet in the upper range, and the playability is excellent.
Best.
Byll
I’m with Byll on this one. The Burkes are really smooth at the top end. Mike has changed the voicing over the years. I keep three non-black tipped Burkes, high D, C and low D, made in 2001 becasue they have the sweetest, easiest high end of any whistles I have ever played. The current Burkes are terrific at the high notes and the low notes are also good and strong.
Feadoggie
helpful info
Although they’re all starting to sound pretty much the same to me (and I have about a hundred whistles), the Sindt and Burke seem sweetest and easiest up there…
Philo
Sindt, Rose, Burke, O’Brien have all been good up top for me.
I’d stay off the Bleazey’s though! 
Interesting the Rose is one of the ones I found to be temperamental at the top , especially the high B
I sat on my Shaw C and bent it by accident. Straightened it up, then squeezed the mouthpiece together to make it need a little less air. All in this is now the easiest instrument i have to hit the high notes. Beautiful beautiful sound. Very quiet even into the lower third octave. Lovely. Its even easier to hit the high notes with this shaw than it is with the sindts (although sindts bring other good things to the party which I like). I have not tried burkes.
Thornton!
Very nice upper register and can be played very softly right up to the top of the second octave without dropping down or squauking.
Owen
My Burke narrow bore is somewhat acceptable in the second octave, but still loud.
I remember my Copeland high D, that one killed elephants. Almost as bad as a Susato.
Whistles that have a distance of less than 5mm from the wind way exit to the blade do ok but can viberate a spider web. Whistles that are very close to 4mm window length can play very sweet to the top. But a lot of players do not take the time to adjust their breath control for the bell note on a whistle like that. Then they say it it is flipping up to soon.